Method for antenna assembly and an antenna assembly with a conductive film formed on convex portions

ABSTRACT

An antenna assembly having patterned conductive films on the surfaces of a dielectric hexahedron with compatibility to mass-production, wherein the conductive films are formed on protuberances formed on the surface of the dielectric hexahedron on which protuberances and depressions are formed. In one embodiment, the dielectric hexahedron includes convex portions serving as the protuberances and concave portions serving as the depressions. A conductive film may be formed on the protuberances by roll coating, sputtering, evaporative deposition, and electroless deposition, thereby producing inexpensively a high quality antenna assembly having a circuit pattern formed thereon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority under 35 U.S.C. §119 toJapanese Patent Application No. 11-202818, filed on Jul. 16, 1999, theentire contents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an antenna assembly comprising ahexahedron of a dielectric material on the surface of which a patternedconductive film is formed.

2. Description of the Related Art

While small size mobile communication sets such as a cordless telephonehave been frequently used in recent years, antennas to be used in thesecommunication sets are required to be compact, highly precise and cheapas other electronic components are.

The main body of this antenna is assembled so that a desired pattern ofa conductive film is formed on each surface of a hexahedron of adielectric material. The conductive film has been formed either byprinting, plating, vapor deposition or sputtering.

In the printing method, however, a complicated and inefficient procedurewas required since the pattern should be independently printed on eachface of the hexahedron. It was also almost impossible to simultaneouslyprint the patterns on plural faces of a polyhedron because simultaneouspositioning of the patterns among printing blocks and plural faces ofthe polyhedron with a high precision was impossible.

The method for forming the conductive film either by plating, vapordeposition or sputtering comprises: a lift-off method in which theconductive film is formed after forming a resist film on the area wherethe conductive film is not formed on each face, followed by removing theresist film; and an etching method in which, after forming a conductivefilm on the entire surfaces on which the pattern is to be formed, apattern of a resist film is formed on the foregoing film, followed byremoving the conductive film in the area not covered with the resistfilm by etching.

However, since both methods described above require to form the resistfilm on each surface on which the pattern is to be formed, it wasdifficult to comply with the requirements of mass-production and lowproduction cost.

SUMMARY OF THE INVENTION

Accordingly, the object of the present invention in view of the problemsas set forth above is to provide a cheap antenna assembly suitable formass-production, wherein a patterned conductive film is formed on thesurface of a dielectric hexahedron.

In one aspect, the present invention for solving the foregoing problemsprovided an antenna assembly comprising a hexahedron of a dielectricmaterial on each surface of which convex portions to serve as a circuitpattern are formed, wherein the circuit pattern comprising a conductivefilm is only formed on the convex portions.

In accordance with another aspect, the present invention provides amethod for manufacturing an antenna assembly, wherein concave and convexportions are machined on the surface of a hexahedron of a dielectricmaterial, and a desired pattern of a conductive film is formed on theconvex portions using a roll coater.

The term “hexahedron” as used herein denotes not only a cube or arectangular parallelpiped column, but also any type of hexahedrons sofar as they have six faces. However, any of the two faces among the sixfaces are preferably in a parallel relation one another in view of thespirit of the present invention. Such hexahedrons having concave andconvex portions formed on the surfaces of a hexahedron such as a cube ora rectangular parallelpiped column, or those having hollow spaces alsobelong to the hexahedron according to the present invention.

While the dielectric material constituting the hexahedron desirablycomprises a ceramic, glass or a mixture of a ceramic and glass in viewof mechanical strength, any dielectric materials may be used so long asit is not contrary to the spirit of the present invention. Accordingly,plastics are acceptable for that purpose.

Although a film comprising a pure metal or metal alloy may beadvantageously used as the conductive film, use of other conductivematerials such as a conductive resin is also possible.

It is desirable in the present invention that the edge angle between thesurface of the hexahedron and the inner wall of the concave portion is80 degree or more and 135 degree or less. The edge may be chipped on theedge when the angle is less than 80 degree while, when the angle islarger than 135 degree, inner faces of the concave portion may becontaminated during deposition of the conductive film to compromise thefunction of the antenna. A edge angle of more than 90 degree and lessthan 120 degree is desirable when the function of the antenna isemphasized.

The conductive film should be continuously formed through the mutuallyadjoining faces on the hexahedron in the present invention, and theedges are desirably chamfered, because the conductive film formed bycoating a conductive paste may be possibly interrupted at the edge whenthe edges are not chamfered. The radius of chamfering is desirably 0.1mm or more and 0.5 mm or less. The effect of chamfering will be invalidwhen the radius of chamfering is less than 0.1 mm, while the conductivepaste can be hardly spread on the chamfered edge during coating torather interrupt the conductive film when the radius of chamfering islarger than 0.5 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of one embodiment of the antennaassembly according to the present invention.

FIG. 2 shows one embodiment of the method for coating the conductivefilm on the antenna assembly according to the present invention using aroll coater.

FIG. 3A shows one of the expanded drawings of the antenna assemblymanufactured by the method according to the third embodiment.

FIG. 3B shows one of the expanded drawings of the antenna assemblymanufactured by the method according to the third embodiment.

FIG. 3C shows one of the expanded drawings of the antenna assemblymanufactured by the method according to the third embodiment.

FIG. 3D shows one of the expanded drawings of the antenna assemblymanufactured by the method according to the third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The embodiment of the present invention will be described hereinafter.

FIG. 1 shows a perspective view representing one embodiment of theantenna assembly according to the present invention. The pattern of theconductive film shown in FIG. 1 is merely one example among existingvarious patterns, and the present invention is never restricted to thepattern as set forth herein. The conductive film may be also formed onthe remaining faces on which the conductive films have not been formedyet, or on the faces having no concave and convex portions, afterforming the convex and concave portions.

The antenna assembly 10 is a hexahedron on the four surfaces 11, 12, 13,and 14 of which concave and convex portions are formed. Conductive films30 (indicated by dotted lines) are formed on the convex portions on thefour surfaces 11, 12, 13, and 14. The dielectric material in thisembodiment comprises a mixture of aceramic and glass, and the conductivefilms 30 comprise an Ag/Pd film.

The surface 12 shown in FIG. 1 serves as an emission pattern face of theantenna, and the surface 13 serves as a power feed pattern face of theantenna. A Short-circuit pattern face and grounding face of the antennaare formed as well on the surfaces 11 and 14, respectively, althoughthey are not illustrated.

Concave portions with a depth of 200 μm are formed on the area notindicated by the dotted lines in this perspective view. Since the Ag/Pdfilm is not deposited on the concave portions, a prescribed pattern thatfunctions as an antenna is formed on the antenna assembly 10. Nomachining is applied on the remaining faces of the hexahedron in thisembodiment.

Subsequently, the first embodiment of the antenna assembly 10 will bedescribed hereinafter.

A mixture of an alumina powder, and two kinds of glass powders ofCaO—Al₂O₃—SiO₂ based and PbO—BaO—SiO₂ based glasses are firstly preparedas a starting material of the dielectric material. The mixed powder iskneaded and granulated after adding water, an organic binder and asurface active agent. The granules are subjected to a press molding thatalso serves for forming concave and convex portions, therebymanufacturing hexahedrons, or rectangular parallelpiped columns, on thesurfaces of which a pattern of the concave and convex portions areformed. After removing the binder from the hexahedron obtained, thehexahedron is fired to manufacture a hexahedron of a dielectricmaterial.

Other method such as a cutting processing, laser processing and etchingprocessing may be also employed for forming the concave portions 20 onthe surface of the antenna assembly 10, other than the press moldingmethod as described above.

Then, conductive films are formed on the four faces 11, 12, 13, and 14of the fired hexahedron using a roll coater shown in FIG. 2. As aresult, the antenna assembly 10 on which conductive films 30 with aprescribed pattern are formed on the convex portions, or the portionsexcluding the concave portions 20, on the surfaces 11, 12, 13, and 14 ofthe hexahedron.

The method for forming the conductive film using the roll coater will bethen described with reference to FIG. 2. FIG. 2 shows a schematicdrawing of the method for forming the conductive film using the rollcoater in FIG. 2.

The roll coater has a pair of rolls 41 and 42 rotating along theopposite directions with each other, and an Ag/Pd paste is coated on therolls 41 and 42. When the conductive film is formed using this rollcoater, an antenna assembly 10 on the surface of which convex portionsand concave portions 20 are formed are inserted between two rollers sothat the surfaces 12 and 14 make slight contact with either the roller41 or the roller 42. Since the Ag/Pd paste only adheres on the convexportions after printing with the roll coater 40, the Ag/Pd filmscomprising a pattern of the emission face and a pattern of the groundingface of the antenna assembly are formed on the surface 12 and on theback face 14.

Subsequently, the antenna assembly 10 is inserted between the rollers ofthe roll coater 40 by allowing the insertion angle of the antennaassembly 10 relative to the roll coater 40 to rotate by an angle of 90degree, to simultaneously print the short-circuit pattern face and thepower feed pattern face of the antenna on the surfaces 11 and 13,respectively, thereby obtaining the antenna assembly on the foursurfaces 11, 12, 13, and 14, of which the Ag/Pd films with desiredpatterns are formed.

A plurality of the antenna assemblies may be simultaneously manufacturedin this embodiment by simultaneously inserting a plurality of antennaebetween the rollers of the roll coater.

Also, it is possible to simultaneously print the patterns on the foursurfaces by using two couples of the pairs of the rollers by allowingone pair of the rollers to be disposed to be perpendicular to the otherpair of the rollers.

The second embodiment of the antenna assembly according to the presentinvention will be described hereinafter.

An antenna assembly fired by the same method as described above is alsoprepared in the method for forming the conductive film in thisembodiment. While the roll coater 40 having the same feature asdescribed above (see FIG. 2) is also used in this embodiment, a solutionof palladium chloride is coated on the roll coater in this method. Theantenna assembly 10 coated with an aqueous solution of palladiumchloride on its convex portions is dipped in a nickel electrolessplating bath (not shown) in the next step to apply nickel plating on theportions where palladium chloride has been coated. In other words theconductive films are formed on the convex portions.

The third embodiment of the method for manufacturing the antennaassembly according to the present invention will be describedhereinafter.

FIGS. 3A to 3D denote expanded drawings of the assembly manufactured inthe third embodiment of the method for manufacturing the antennaassembly according to the present invention.

The expanded drawings of the assembly manufactured in the thirdembodiment of the method for manufacturing the assembly 50 according tothe present invention are illustrated in FIGS. 3A to 3D.

The assembly 50 comprises a hexahedron of a ceramic, wherein concaveportions 60 (the portions not indicated by the dotted lines) with awidth of 200 μm and a depth of 400 μm are formed on the surface 52 amongthe four surfaces 51, 52, 53, and 54. An aluminum film 70 (the portionsindicated by the dotted lines) that is a different material from theconstituting material of the assembly 50 is formed on the portions ofthe surface 52 excluding the concave portion 60. The surface 52 shown inFIG. 3B corresponds to a top face of the assembly 50, while the surface54 shown in FIG. 3D denotes a bottom face. A plurality of theseassemblies were arranged along the horizontal direction with the surface52 as the top face upward, and the Al film was formed by sputtering onthe five surfaces of each antenna assembly except the surface 54 as abottom face. Although the Al film was adhered on a part of the innerwall face of the concave portion, no film adhered on the wall face at adepth of 200 μm or more, indicating that patterned films can be formedon the surface of the polyhedron by the method for manufacturing theassembly according to the present invention. Such assembly as describedabove can be machined to utilize it as an antenna assembly.

The same result as described in the third embodiment can be alsoobtained when the Al film is deposited by using a vapor depositionmethod, instead of the sputtering method used in the third embodiment.

The conductive films are formed only on the convex portions of thehexahedron of the dielectric material on the surface of which theconcave and convex portions are formed in the antenna assembly accordingto the present invention. Consequently, the conductive films that areessential for the antenna assembly can be precisely and easily depositedto enable the good quality antenna assembly to be cheaply manufacturedin large scale.

What is claimed is:
 1. A method for manufacturing an antenna assembly, comprising: machining concave portions and convex portions on the surface of a hexahedron of a dielectric material; and forming a desired pattern of a conductive film over an entirety of the convex portions using a roll coater, without forming the conductive film on the concave portions.
 2. An antenna assembly, comprising: a dielectric material having a plurality of surfaces, at least one surface thereof serving as an emission pattern face, at least one surface thereof including a protruding portion in the dielectric material that substantially defines a circuit pattern and a non-protruding portion, and at least one surface serving as a power feed pattern face, and at least one surface serving as a grounding pattern face; and a conductive film substantially formed over an entirety of said protruding portion and at least one other surface of said plurality of surfaces, without forming the conductive film on the non-protruding portions.
 3. The assembly of claim 2, further comprising: an adhesion layer substantially formed between said protruding portion and said conductive film.
 4. The assembly of claim 3, wherein said adhesion layer comprises palladium chloride.
 5. The assembly of claim 2, wherein said conductive film comprises an electroless film.
 6. The assembly of claim 5, wherein said electroless film comprises a nickel electroless film.
 7. The assembly of claim 2, wherein said at least one surface further comprises a recessed portion.
 8. The assembly of claim 7, wherein said recessed portion comprises a depression extending from a plane including said at least one surface into said dielectric material.
 9. The assembly of claim 2, wherein said protruding portion comprises a protuberance projection above a plane including said at least one surface.
 10. A method for manufacturing an antenna assembly, comprising steps of: forming on at least one surface of a dielectric material a protruding portion in the dielectric material substantially defining a circuit pattern and a non-protruding portion; and coating an entirety of said protruding portion and at least one further surface with a conductive film, without coating the conductive film on the non-protruding portion.
 11. The method according to claim 10, wherein said forming said protruding portion comprises a step of press molding said dielectric material in a mold.
 12. The method according to claim 10, wherein said step of forming said protruding portion comprises etching a recessed portion of said dielectric material.
 13. The method according to claim 10, wherein said coating said protruding portion comprises a step of roll coating said conductive film.
 14. The method according to claim 10, wherein said coating step comprises sputtering said conductive film, and said step of forming a protruding portion comprises forming a recessed portion deeper than a thickness of said conductive film.
 15. The method according to claim 10, wherein said coating step comprises vapor depositing said conductive film, and said step of forming a protruding portion comprises forming a recessed portion deeper than said conductive film is thick.
 16. The method according to claim 10, wherein said coating step comprises: forming an adhesion layer on said protruding portion; and electrodepositing said conductive film on said adhesion layer.
 17. The method according to claim 16, wherein said step of forming an adhesion layer comprises a step of roll printing said adhesion layer.
 18. The method according to claim 10, further comprising a step of chamfering an edge where said at least one surface and a second surface of said dielectric material meet.
 19. The method according to claim 16, wherein said adhesion layer comprises palladium chloride.
 20. An antenna assembly comprising a hexahedron having a surface on which convex portions to serve as a circuit pattern and concave portions are formed, and having at least one surface thereof serving as an emission pattern face; and a conductive film formed over an entirety of the convex portions without being formed on the concave portions. 